Micro-cantilevers find use in many applications. For example, the atomic force microscope has for some time used deflection of a micro-cantilever to measure the force between the cantilever tip and the sample. More recently, arrays of micro-cantilevers have been used as biosensors. It has been shown that when biochemically specific interactions occur between a ligand immobilized on one side of a micro-cantilever and a receptor in solution, the micro-cantilever bends, which can be detected optically.
International patent application WO02008129272 describes an apparatus for measuring changes in shape of tethered or untethered cantilevers. As described, a Fraunhofer interference pattern is formed by light transmitted through or reflected from a cantilever. Changes in the shape of peaks and/or troughs in the interference pattern relative to the interference pattern for an undistorted cantilever are analysed to obtain information about changes in the cantilever shape.